Which of the following is non-stoichiometric?

Zinc oxide (white) is heated to high temperature for some time. Observe the following statements regarding the above process:
$I$. Zinc oxide colour changes to pale yellow
$II$. The type of defect formed is 'metal deficiency'
$III$. Some $Zn^{2+}$ and $e^{-}$ are present in interstitial places
The correct statements are:

Identify the defect that develops when the ratio of number of cations to anions becomes different from that indicated by its chemical formula.

Which among the following statements is $NOT$ true about Frenkel defect?

$A$ sample of ferrous oxide has actual formula $Fe_{0.93}O_{1.00}$. In this sample,what fraction of metal ions are $Fe^{2+}$ ions? What type of non-stoichiometric defect is present in this sample?

The formula of a metal oxide with a metal deficiency defect in its crystal is $A_{0.8}O$. The crystal contains $A^{2+}$ and $A^{3+}$ ions. The fraction of metal existing as $A^{2+}$ ions in the crystal is -